1. Field of the Invention
The present invention relates to a method for manufacturing semiconductor device. More particularly, the present invention relates to a method for manufacturing semiconductor device and non-volatile memory.
2. Description of the Related Art
Non-volatile memory is a type of memory that has the capacity to retain stored data even after power to the device is removed. Because non-volatile memory products such as flash memory and nitride read-only-memory (NROM) allow multiple data entry, reading and erasing operations, these memory devices have been broadly applied in personal computer and electronic equipment.
FIG. 1A is a top view of a conventional non-volatile memory. FIG. 1B is a schematic cross-sectional view along line I–I′ (the X direction) of FIG. 1A and FIG. 1C is a schematic cross-sectional view along line II–II′ (the Y direction) of FIG. 1A. The conventional method of fabricating the non-volatile memory includes providing a substrate 100 and then forming a plurality of gate lines 102 on the substrate 100 with spacers 104 on their respective sidewalls. Each gate line 102 includes a dielectric layer 103, a gate 105 and a cap layer 107. Then, a dielectric layer 106 and a conductive layer (not shown) are sequentially formed over the substrate 100.
Thereafter, a portion of the conductive layer is removed to form a plurality of gates 110 that completely fills the gaps between the gate lines 102. The gates 110 and the gate lines 102 together form memory cell rows 113. Furthermore, conductive spacers (not shown) are also formed on the sidewalls of the outermost gate lines 102. A silicon oxide layer 115 is subsequently formed on the surface of the gate 110. After that, a patterned photoresist layer (not shown) is formed over the substrate 100 and an etching operation is carried out to remove the conductive spacers. Finally, source/drain regions 114 are formed in the substrate 100 on the respective sides of the memory cell rows 113.
However, in the aforementioned process, a silicon oxide layer is formed on the conductive spacers. As a result, the etching operation for removing the conductive spacers can hardly remove all the conductive spacers. The remaining polysilicon residue 116 often leads to a short circuit in the semiconductor device.